This invention relates to fabrication and testing of magnetic head suspension assemblies.
FIG. 1 shows a fragmentary view of a prior art disk drive having an actuator arm assembly 2 and a stack of spaced apart disks 4 rotatable about a common spindle 5 as represented by the arrow 20. The actuator arm assembly 2 is also rotatable about an actuator arm axis 6. The arm assembly 2 includes a plurality of actuator arms 8A-8C which extend into the spaces between the disks 4A and 4B. Attached to each of the actuator arms 8A-8C is a magnetic head suspension assembly 10, which comprises a resilient load beam 12, a flexure 14 and a slider 16. Each load beam 12 is attached to one of the actuator arms 8A-8C via a base plate 25 having a boss 40 snugly inserted into the actuator hole 42 as shown in FIG. 1.
FIG. 2 shows the magnetic head suspension assembly 10 in further detail. The load beam 12 is made of resilient material which is slightly bent toward the disk surface 18 (FIG. 1). Underneath the distal end of the load beam 12 is the flexure 14. An alignment hole 33 in the load beam 12 is provided for the alignment of the corresponding hole in the flexure 14, thereby orienting the flexure 14 in a proper location. The flexure 14 is fixedly attached onto the load beam 12 in the area surrounding the alignment hole 33 via welding.
The flexure 14 has an integrally formed tongue portion 26. Fixedly attached to the tongue portion 26 is the slider 16. Stamped at the end of the load beam 12 is a dimple 28 which is urged against the tongue portion 26 of the flexure 14. The dimple 28 acts as the fulcrum for the resilient flexure 14 to provide gimbaling action. At the edge of the slider 16 is a magnetic head transducer 24. Electrical signals written in or read out of the transducer 24 are conducted by wires 30 disposed on the load beam 12 and guided by one of the load beam ribs 32A. As an alternative, a flex circuit 34 is used in lieu of the wires 30. Instead, electrical signals are sent or received through the traces 36 (shown partially as a representation in phantom) embedded on the flex substrate 38 of the flex circuit 34.
The topology of the disk surface 18, though highly polished, is not at all uniform at microscopic scale. Very often, the disks 4A and 4B are not rotating about the spindle at a perfectly perpendicular angle. A minute angular deviation would translate into varying disk-to-slider distances while the disks 4A and 4B are spinning. For reliable data writing and reading, the slider 16 thus has to faithfully follow the topology of the spinning disks 4A and 4B, without ever contacting the disk surfaces 18. The head gimbal assembly 22 is employed to accommodate the disk surface topology. Basically, the gimbal assembly 22 is designed to dynamically adjust the position of the slider 16 to conform to the irregular disk surface 18 while the disk is spinning. To meet this end, the flexure inside the gimbal assembly 22 must be sufficiently flexible and agile on one hand, yet stiff enough to resist physical deformation on the other hand.
The magnetic suspension assembly 10, which includes the slider 16, the flexure 14,the load beam 12, the baseplate 25, and either the wires 30 or the flex circuit 34, needs to be tested prior to installation to a disk drive. Heretofore, testing of the magnetic head suspension assembly 10 involved inserting the entire assembly 10 into the arm of a spin station which performs the tests. Of all the constituent parts of the suspension assembly 10, the transducer 24 is the most delicately fabricated component. Often, the failure of the assembly 10 is the electrical malfunctioning of the transducer 24. Since the magnetic head suspension assembly 10 is permanently attached, the entire assembly 10 has to be rejected as a consequence.
The technological trend in disk drive manufacturing is toward miniaturization. As a consequence, sliders are reduced in size. A fixed area of a wafer can now yield more sliders than in the past. Accordingly, costs for each slider fabricated with the transducer 24 decrease. Instead, a greater portion of the manufacturing cost shifts to the other components of the assembly 10. Thus, rejecting the entire assembly 10 which includes the base plate 25, the load beam 12, the flexure 14 and the flex circuit 34 is wasteful and unnecessarily increases manufacturing costs.
There is also a trend toward new designs which include active integrated circuits (not shown) disposed near the transducer 24. For example, integrated circuits may be placed on the flex circuit 34 or the load beam 12. Weak signals picked up by the transducer are immediately amplified by the integrated circuits before the next stage of signal amplification during data reading, for instance. Placing the active circuits close to transducer 24 substantially improves the signal-to-noise ratio (SNR) of the magnetic head assembly 10. Adopting the prior art approach of testing and manufacturing of the assembly 10 would further aggravate the situation and is even more wasteful because the active circuits also need to be discarded in the event of test failure. Accordingly, there has been a long-felt need for building magnetic head suspension assemblies without the aforementioned problems.
It is an object of the invention to provide a method of prescreening defective components prior to final assembly in the manufacturing of magnetic head suspension assemblies, thereby improving production yield and reducing manufacturing costs.
In accordance with the invention, a slider is fabricated with a magnetic head transducer and then attached to an intermediate flexible circuit. The combination is thereafter inserted into a spin stand tester for the testing of various electrical parameters. If the attached combination fails the test, it is discarded. On the other hand, if the attached combination passes the test, it is mounted onto a load beam to form the magnetic head suspension assembly. In one embodiment, the intermediate flexible circuit affixed with the slider is attached to a load beam having a flexure. In another embodiment, the intermediate flexible circuit is attached to a load beam having no pre-disposed flexure, wherein the intermediate flexible circuit acts as the flexure in the final assembly.
Accordingly, the magnetic heads, which normally experience the highest failure rate, are isolated and rejected prior to final assembly, without affecting the associated components which are more expensive.